Use of near-infrared (NIR) transmittance spectroscopy for rapid determination of the oxidation level in soybean oils (SBO) was investigated, and calibrations were developed for quantitative determination of peroxide value (PV), conjugated diene value (CD), and anisidine value (AV) of SBO. Partial least squares (PLS) regression and forward stepwise multiple linear regression were used to develop calibration models from spectral data in log 1/T, first derivative and second derivative of log 1/T formats for both 1-and 2-mm path lengths. The models were validated by comparing NIR results from independent sample sets to the values obtained by official methods. The spectral region from 1100 to 2200 nm was best for measuring oxidation when using a 2-mm path length. PLS regression using first-derivative spectra gave the best results for PV. For the validation sets, linear relationships were obtained for PV (r = 0.99), and CD (r = 0.95), compared with accepted reference procedures. However, measurement of AV by NIR was less successful than measurement of the other two indices of oxidation, especially for an external validation sample set. Results obtained in this study indicate that NIR spectroscopy is a useful technique for measuring oxidation in soybean oil.Paper no. J9687 in JAOCS 78, 495-502 (May 2001).

Previous work in our laboratory demonstrated that soybean oil oxidation, expressed as PV, can be determined using NIR transmission spectroscopy as an alternative to the official AOCS iodometric titration method. In the present study, a comparison of four peroxide analytical methods was conducted using oxidized soybean oil. The methods included the official AOCS iodometric titration, the newly developed NIR method, the PeroxySafe™ kit, and a ferrous xylenol orange (FOX) method, the latter two being colorimetric methods based on oxidation of iron. Five different commercially available soybean oils were exposed to fluorescent light to obtain PV levels of 0-20 meq/kg; periodic sampling was done to ensure having representative samples throughout the designated range. A total of 46 oil samples were analyzed. Statistical analysis of the data showed that the correlation coefficient (r) and standard deviation of differences (SDD) between the standard titration and NIR methods were r = 0.991, SDD = 0.72 meq/kg; between titration and the PeroxySafe™ kit were r = 0.993, SDD = 0.56 meq/kg; and between the standard titration and FOX method were r = 0.975, SDD = 2.3 meq/kg. The high correlations between the titration, NIR, and PeroxySafe™ kit data indicated that these methods were equivalent.

NIR spectroscopy was used successfully in our laboratory to monitor oxidation levels in vegetable oils. Calibration models were developed to measure PV in both soy and corn oils, using partial least squares (PLS) regression and forward stepwise multiple linear regression, from NIR transmission spectra. PV can be measured successfully in both corn and soy oils using a single calibration. The most successful calibration was based on PLS regression of first derivative spectra. When this calibration was applied to validation sample sets containing equal numbers of corn and soy oil samples, with PV ranging from 0 to 20 meq/kg, a correlation coefficient of 0.99 between titration and NIR values was obtained, with a standard error of prediction equal to 0.72 meq/kg. For both types of oil, changes occurred in the 2068 nm region of the NIR spectra as oxidation levels increased. These changes appear to be associated with the formation of hydroperoxides during oxidation of the oils.Existing analytical procedures for measuring the oxidation level in vegetable oils are time consuming, destructive to the sample, and costly, and they require large amounts of glassware, lipids, and potentially hazardous reagents. NIR spectroscopy, which can overcome many of these drawbacks, has many applications in the food industry, including fat and oil quality evaluation. In the recent past, a number of new spectroscopic methods have been developed for measuring lipid oxidation (1-5). These methods are simple, fast, and safe, and they dramatically reduce the labor and solvent needed. Previous work in our laboratory demonstrated that soybean oil oxidation, expressed as PV, can be determined successfully using NIR transmission spectroscopy as an alternative to the official AOCS iodometric titration method, and satisfactory repeatability was obtained by both methods (6).In the present study, NIR spectroscopy was examined as a possible alternative to the conventional titration method for determining oxidation levels in corn oils, and calibrations were developed for quantitative determination of PV of corn oils. Additionally, the potential of using a single calibration to measure oxidation in oils from multiple sources was evaluated. Therefore, the objectives of the present research were threefold: (i) to investigate the relationship between NIR spectra and lipid oxidation in corn oil; (ii) to evaluate the success of the NIR models developed by testing each with an independent set of corn oil samples; and (iii) to create and evaluate calibrations encompassing both soybean oil and corn oil. EXPERIMENTAL PROCEDURES Selection of corn oil samples. Commercial corn oils (CO)were used for calibration development and validation. To achieve variation in the oils, five CO representing four commercial brands with different "sell by" dates and batch codes were purchased from local supermarkets in Lincoln, Nebraska. Samples with a range of oxidation levels as measured by PV were then prepared by subjecting each corn oil to fluorescent light for varying lengths ...

Treatment of PKU (Phenylketonuria) is a lifelong special diet program starting from the newborn period. The aim of this study was to produce an alternative product for PKU patients. Low protein milk substitute, xanthan gum (1%), Nestle nestergel yoghurt gelling agent (1.5%), starch (4%) and pectin (1.6%) were used to produce yoghurt substitue. Control yoghurt was produced from cow's milk. The fermentation of all samples was completed at the end of the 5th hour. The pH of the samples decreased during storage. The total solid matter of the corn starch and pectin added samples were higher than the others. Syneresis values of the samples with xantan gum, pectin and nesterjel were 0% or close to 0%. The shear stress of xantham gum, nestergel, starch added samples were found close to each other. The shear stress of the pectin added sample was higher than for them. L* values of the control and starch added samples, a* and b* values of pectin added sample were higher than those of other samples. The amount of protein and Phe was significantly higher in the pectin added sample than the other samples (p